1. Field of the Invention
This invention is related in general to autonomous vehicles and other equipment operating in a surface facility and, in particular, to a system for controlling the interaction among autonomous vehicles and between autonomous and manned vehicles to ensure safety and efficiency in a surface mine.
2. Description of the Related Art
It is known that traffic of manned or autonomous vehicles in a system can be controlled by tracking the position of each moving component in the system and by communicating with each vehicle from a central location, from a peripheral position, or directly from other vehicles, to guide the vehicle safely along a desirable course. Air-traffic control systems represent a good example of such an approach. The position of each aircraft is continuously monitored by one of many air-traffic control centers that is also in constant communication with the aircraft, ready to alert its crew of any impending danger or other situation deserving of attention. When the aircraft is unmanned, the communication includes control signals to an on-board computer that controls the flight of the craft through appropriate software and electronic and mechanical hardware. That is how an unmanned spacecraft is guided in flight. Thus, for the purposes of this disclosure, the term xe2x80x9cautonomousxe2x80x9d is intended to refer to the availability of either on-board or off-board supervisory systems for directing and/or controlling the movement of a vehicle.
Surface mines utilize a variety of work machines for excavating and transporting ore, grading and stabilizing roadways and slopes in the mine pit, and for providing all support functions necessary for the operation of a mine. Most work and haulage machines have been human-operated in the past, as mobile pieces of equipment constantly being maneuvered around the surface of the mine. Skilled operators ensure that each machine or vehicle is positioned in the right place and optimally oriented to perform its intended function while avoiding accidents and injury to people and property. In order to improve efficiency, much effort is currently under way to develop automated systems for controlling the operation of such work machines in surface mines and other similar environments.
Autonomous vehicles in a surface mine operation include mechanical hardware, a computer and appropriate software for implementing the various functions of the machine in response to control inputs provided by a control system. In a fashion similar to the guidance of unmanned aircraft, an autonomous vehicle can be monitored and guided by a central or satellite center transmitting control signals to the vehicle""s on-board computer based on current mine conditions and in response to position data communicated by the vehicle. Knowing the current position of the vehicle with respect to known fixed obstacles and other mine equipment, the vehicle can be maneuvered to destination by the continuous control of its operating functions (for example, steering-wheel, accelerator and brake position of a truck). An on-board satellite-based positioning system (such as GPS) or an equivalent positioning unit (either of which can be supplemented with an inertial navigation system or the like) can be used to determine the current position of the vehicle, with an on-board transmitter/receiver unit to communicate with the control center, and on-board microprocessing and storage modules with appropriate hardware and software to effect the actual movement of the vehicle. Every operating function is manipulated to cause the vehicle to follow a predetermined course or set of courses modified according to current control instructions to meet particular up-to-date traffic conditions. Hazards can be avoided by implementing a predetermined control response when a hazard is identified by the system. For example, if a potential obstacle is detected within a certain distance of the vehicle being monitored, the course of the vehicle can be modified to avoid a collision.
This approach to traffic control has been found to be effective for systems operating at near steady state most of the time, just as in the case of airplanes that follow predetermined flight paths from a starting point to a destination. When rapidly changing conditions exist, though, such as within the traffic of a surface mine where multiple vehicles and other equipment cross paths and change direction and speed as required to perform multifaceted functions and to meet continuously changing optimal mine-operation alternatives, such a rigid, strictly reactive system of accident prevention is not adequate. A large degree of flexibility is required to distinguish between different kinds of hazards. For example, while an unidentified obstacle approaching a vehicle traveling at 30 miles per hour along a predetermined path on a mine road may warrant the immediate stoppage of the vehicle, the approaching of a known potential obstacle, such as another vehicle traveling in the opposite direction, may only require a reduction in speed and an additional precautionary adjustment, such as a shift to the appropriate side of the roadway.
In U.S. Pat. No. 5,629,855, Kyrtsos et al. describe a novel parabolic model and processing algorithm for predicting the path and updating the position of an autonomous vehicle based on a combination and filtering operation of previously acquired position values. In the course of explaining the invention, the patent describes many conventional features of autonomous-vehicle systems. For example, it discloses the use of travel-route components assigned to each vehicle to control its motion so as to conform to a target trajectory between locations. The routes are subdivided into segments or paths between fixed nodes along the target trajectories, and these segments are used to progressively effect the travel of the vehicle according to conventional motion-control techniques. Similarly in conventional fashion, typical operational constraints, such as speed limits, are associated with each segment for the performance of predetermined tasks in a safe and/or optimal manner by each vehicle along the assigned trajectories.
Commonly owned U.S. patent application Ser. No. 09/521,436, hereby incorporated by reference, describes a mine traffic and safety control system where the function of each autonomous vehicle is also performed according to a predetermined trajectory related to its particular task and implemented with on-board GPS and two-way communication hardware. The current position of the vehicle is continuously monitored and correlated to the position of potential hazards along its path, so that corrective action can be taken by implementing appropriate, predetermined control strategies. Each vehicle is assigned a xe2x80x9csafety envelopexe2x80x9d that allows for the vehicle""s physical presence and operating tolerances. The safety envelope is characteristic of each vehicle and is defined by a variable space surrounding the vehicle wherein it may be physically present as it travels along its intended course. The shape and size of the safety envelope is dynamically varied to meet safety requirements for current course conditions facing the vehicle as it performs its autonomous function along its predetermined path. The safety envelope is changed according to a predetermined set of rules specific to the vehicle. Intersection locations among the various courses potentially followed by vehicles along roadways and other sites within the mine""s property are established dynamically by monitoring current traffic conditions and identifying situations where the safety envelopes of vehicles traveling along approaching courses could overlap.
This concept of xe2x80x9csafety envelopexe2x80x9d superimposed over conventional notions of motion guidance over a predetermined travel trajectory is one component of a new approach to provide a mine traffic and safety control system capable of flexible, dynamic response. The present invention discloses another component in the implementation of such a system. The invention relates to the notion of subdividing the affected territory into zones of free operation, denoted permission zones, wherein each vehicle is allowed to move freely so long as it conforms to safety and other operational constraints pertaining to that zone. A permission zone always corresponds to a territory that is free of obstructions to travel, such that a vehicle can safely move anywhere within the zone, but it may or may not overlap a predetermined travel trajectory for the vehicle. Similarly, a permission zone may encompass portions of more than one trajectory; that is, alternative routes for moving an autonomous vehicle between locations. By assigning permission zones to autonomous vehicles, an additional layer of control is attained over the prior-art type of constraints imposed by conventional tracking systems and guidance algorithms, which are still also retained in the traffic system of the invention in order to guarantee absolute safety while ensuring optimal efficiency of operation. The invention is described in the context of a surface mine operation, but its concept is applicable to any operation involving moving equipment (such as waste sites, underground mines, quarries, warehouses, and the like), and should not be limited to surface mines.
The primary, general objective of this invention is an independent and supervisory safety system, used in addition to conventional guidance and alarm systems and apparatus, for monitoring and controlling traffic in order to guarantee the avoidance of hazards by all autonomous vehicles and equipment operating at a surface mine.
Another general objective is an approach that permits the dynamic adaptation of safety and operational control rules to current circumstances facing a moving vehicle in a mine.
Another, more specific, goal of the invention is a system that provides an autonomous vehicle with an exclusive zone of free operation, so that the vehicle is allowed a predetermined operating space for carrying out its task in optimal fashion without interference from potential collision hazards independently of all other safety controls and/or constraints imposed by the vehicle guidance system.
Still another objective is an approach that is compatible with an overall hazard avoidance system that utilizes apparatus implementated through removable modules for each autonomous vehicle.
Another goal is a system that is suitable for automated implementation with current surface-mine haulage and mining equipment.
A final objective is a system that can be implemented economically according to the above stated criteria.
Therefore, according to these and other objectives, the broad embodiment of the present invention requires linking each autonomous vehicle and/or other moving equipment in a surface-mine facility to a control center for communicating data and control signals. Using on-board computer, GPS and two-way communication hardware, the function of each autonomous vehicle is performed through a conventional guidance system by causing the vehicle to follow a trajectory along a course or path related to its particular task. The current position of the vehicle is continuously monitored and correlated to the position of potential hazards along its path, so that appropriate traffic-control guidance can be implemented and corrective action can be taken, when needed, according to predetermined control strategies.
Specifically, one novel aspect of the present invention consists of dividing the mine territory into areas that contain parts of the mine open to traffic along each course potentially followed by a vehicle following an assigned trajectory. Each area is treated as an exclusive zone of free operation (defined as a xe2x80x9cpermission zonexe2x80x9d) wherein the vehicle is allowed to move according to predetermined permission parameters but unhindered by other system constraints and clear of other vehicles in the system. A permission zone is established dynamically as a function of the current position of all vehicles over the territory and according to criteria that ensure no collision can occur so long as each vehicle acts within such predetermined permission parameters. Before it can begin to move, each vehicle is assigned at least one permission zone (which therefore becomes an active permission zone) that includes the vehicle""s current location and excludes the current location of all other autonomous vehicles in the system.
According to another aspect of the invention, each active permission zone (or sequence of permission zones) is associated with a permission parameter consisting of a maximum velocity profile that ensures stoppage of a vehicle prior to or at the boundary of the permission zone (or the end of the last active permission zone in a sequence of adjacent zones). In order to produce an efficient flow of traffic at maximum speeds, subsequent permission zones are assigned to a vehicle sequentially as early as possible and the velocity profiles are updated correspondingly on a current basis to allow full speed until the end of the last active zone. Successive permission zones along a predetermined course are assigned to a vehicle as soon as the position of all other vehicles and all other system constraints make them available.
Thus, according to the invention, vehicle traffic is first controlled by the current, ongoing assignment of active permissions zones, which are continuously monitored for availability on the basis of all other vehicles"" movements and other operational constraints built into the system. The subsequent motion of each vehicle along its intended trajectory is advantageously controlled with the further assignment of permission zones, a feature that affords a real-time dynamic adjustment to varied traffic conditions and a corresponding degree of improved flexibility. By combining the allocation of active permission zones with conventional safety and guidance-control mechanisms associated with each travel trajectory, an additional layer of safety is superimposed over the overall traffic guidance system of the prior art.
Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose but one of the various ways in which the invention may be practiced.